Diverse antigens via IgG Fab regions (IgG Fab)

Diverse antigens via IgG Fab regions is a pharmacological classification used to describe the collective molecular targets recognized by the Fragment antigen-binding (Fab) domains of pooled human Immunoglobulin G (IgG), typically administered as Intravenous Immunoglobulin (IVIG) [Source: IUPHAR/BPS Guide to PHARMACOLOGY]. Unlike monoclonal antibodies that target a single specific epitope, the Fab regions in these polyclonal preparations represent a vast repertoire of specificities derived from thousands of healthy donors. These Fab regions function by binding to and neutralizing a wide array of exogenous antigens, such as bacterial toxins and viral particles, as well as endogenous targets like pro-inflammatory cytokines and pathogenic autoantibodies [PMID: 23433515]. This broad-spectrum binding is essential for providing passive immunity in patients with primary immunodeficiencies and for modulating the immune system in autoimmune and inflammatory diseases like Kawasaki disease and Idiopathic Thrombocytopenic Purpura (ITP) [PMID: 21223921]. While the Fc portion of the IgG molecule also mediates critical immunomodulatory functions through Fc receptors, the Fab-mediated interactions are the primary drivers of the therapy's direct neutralizing and anti-idiotypic effects.

Other names

Polyclonal IgG targetsIVIG antigensAntigen-binding fragments of pooled IgGNormal immunoglobulin targetsFab-mediated antigen binding

Neutralization of exogenous pathogens (viruses, bacteria) and toxins via high-affinity Fab-mediated binding; anti-idiotypic neutralization of pathogenic autoantibodies; and modulation of inflammatory cytokine signaling [Source: PMID: 23433515, PMID: 21223921].